A knitting machine of this kind, such as that described in U.S. application Ser. No. 438,890, filed Oct. 21, 1982, now Pat. No. 4,532,781, to which German Patent Disclosure Document No.DE-OS 31 08 041 corresponds, is distinguished by a high operating speed. The hold-down and knock-over sinkers are moved longitudinally, counter to the needle casting-off movement, after the operation of latch clearing or holding down has been performed, or in other words during the actual process of loop formation. As a result, the distance the needles must travel during the casting-off movement becomes correspondingly shorter, so the needle cam race can be embodied with a less steeply inclined surface. This makes it possible to increase the knitting speed substantially. The transverse movement of the sinkers with respect to the associated needles that takes place after the holding down operation serves to move the sinkers into the correct position for knocking over. After the loop forming process has ended, when the needle is again projected, the corresponding sinkers are returned to the initial position, counter to the projection movement of the needles; in so doing, the sinkers are first moved transversely to the needles so as to hold down the half-finished row of loops and prevent the goods from being pulled along with the needles as they are projected.
The longitudinal sliding movement of the combined hold-down and knock-over sinkers is effected via control butts disposed on the ends of the sinker shanks, which cooperate with associated sinker cam races disposed in a cam box below the needle cam race. A further circumferential sinker cam race of tapering cross section is disposed above the needle cam race; it is traced by corresponding noses, disposed such as to protrude laterally on the sinker shanks, in order to generate the transverse movement of the hold-down and knock-over sinkers, the fulcrum of which is disposed on the end of the sinker shank carrying the control butt.
In this knitting machine, the sinker shanks directly embody the guide ribs for the needle shanks, producing a very fine needle cut, the minimum limit of which is dictated only by the thickness of the hold-down and knock-over sinkers.
Since the surfaces of the sinker cam race, which in cooperation with the control butts generate the longitudinal movement of the sinkers, are located below the needle cam race, the hold-down and knock-over sinkers must have relatively long shanks. If patterning devices are associated with the needles, then a plurality of needle cam races disposed one above the other must be used, cooperating with the correspondingly arranged butts of the various types of needles required in that case. This means that more space is then required, which in turn dictates a further lengthening of the sinker shanks.
However, long sinker shanks produce a considerable amount of frictional heat as they move, and dispersing this heat can become problematic in machines that operate at very high speed. Furthermore the forces of acceleration and deceleration that arise with the sinkers, which have relatively great masses, become undesirably large.
The same basic situation exists in a knitting machine operating on the same principle and disclosed in U.S. patent application Ser. No. 559,495, filed Dec. 8, 1983, now U.S. Pat. No. 4,546,623, by Kuhn and Buck, which is part of the prior art here and in which each of the hold-down and knock-over sinkers has a shank embodied as a two-armed lever. This shank is supported on the needle bed on a fulcrum with a crosswise axis, and two sinker cam race surfaces are provided on both sides of the fulcrum, each acting on one of the lever arms. With these surfaces, it is possible to generate a transverse movement of the head of the hold-down and knock-over sinker in one direction by means of one surface and in the opposite direction by means of the other. Once again, in this knitting machine, the sinker cam race surface that generates the longitudinal movement of the sinkers, like one of the sinker cam race surfaces that generates the transverse movement of the sinker head, is located below the needle cam race, so that once again the sinker shanks have a relatively great length.
In knitting machines operating with hooked sinkers for spreading apart and taking on the latest loops formed at a particular time, it is known (German Patent Disclosure Document No. DE-OS 29 09 963) to dispose the sinker cam race surfaces above the needle cam race, thereby resulting in a relatively short length for the shanks of the hooked sinkers, which are pivotable about a horizontal axis at a fulcrum. The hooked sinkers have a transporting hook that extends in the longitudinal direction of the shank, and the section that bears the transporting hook is joined to the shank via a resilient part. The sinkers are supported on the associated needle shank, which in turn is laterally guided between ribs of the needle cylinder. The hooked sinkers, which are pressed with spring biassing against the backs of the needle shanks, again generate considerable friction, however, and also place a strain on the needle shanks, which can cause problems in very high-speed machines.